Demm,
Many thanks for the feedback, I'll put this subject to sleep now.
But to to clarify my mention of Calamares was wrong, it's just that the initial boot screen displays the choices differently, depending on what system and screen size.3840x2160 or 1920x1080.
Both the 20.2020 ISO and the 07.2020 ISO give identical output when running "hwdetect".
Also the latest Arch Linux installation ISO with kernel 5.7.11 loads OK with no errors, haven't tried the full install yet but will do.
Many thanks again I shall look forward to trying the next ISO.